The present invention builds on a method for vacuum treatment or on a method for producing powder.
According to the present invention a vacuum treatment installation is obtained, as well as used.
The present invention, in principle, has the objective of reactively depositing plasma-enhanced, i.e. through a PECVD method, materials on a deposition surface, be these materials which generally are extremely difficult to produce, namely metastable materials such as cBN, xcex1-Al2O3, C3N4 or, in particular, diamond materials, or basically materials at maximally high deposition rates and at maximally low temperatures, in particular when Si-containing compounds, further particularly microcrystalline xcexcCxe2x80x94Si:H, are to be deposited.
EP 0 724 026 by the same applicant as the present invention, corresponding to U.S. Pat. No. 5,753,045, discloses a method for the vacuum treatment of at least one workpiece, in which the workpiece is exposed in a vacuum atmosphere to a reactive gas excited by means of a plasma discharge. The workpiece surfaces to be coated are disposed offset with respect to the plasma beam axis such that thereon a plasma density obtains of maximally 20% of the maximum density obtaining in the plasma beam axis. This procedure permits deposition layers difficult of production, in particular those comprising metastable materials in particular of diamond, cBN, xcex1-Al2O3 or C3N4. With respect to the definition of xe2x80x9cmetastable materialsxe2x80x9d, reference is made to xe2x80x9cLehrbuch der anorganischen Chemiexe2x80x9d, Hohlemann-Wiberg, Walter Gruyer, Berlin, N.Y. 1976, Edition 81-90, p. 183 ff, which is to say materials which are deposited in a slightly reversible reaction.
According to the Swiss Patent Application 794/99 by the same applicant as the present invention, it has been recognized that said methodxe2x80x94according to EP 0 724 026xe2x80x94surprisingly is also suitable for high-rate coating of surfaces, on the one hand, and for generating powder or cluster-form material on a collection surface, on the other hand.
Of disadvantage in these prior known processes is that therewith, on the one hand, only workpiece surfaces of relatively small, in particular planar, dimensions can be homogeneously treated, in particular coated, but that, on the other hand, it would be entirely desirable to increase the quantity of powder or clusters generated per unit time. Consequently, it would be desirable to realize, in particular for diamond coating, a relatively large-area, uniform layer thickness distribution also at maximally high coating rates.
The objective of the present invention is to attain such.
For this purpose the method according to the invention for the treatment of workpiecesxe2x80x94also as a basis for the installation according to the invention is distinguished because, in the vacuum atmosphere, at least two plasma beams with substantially parallel beam axes are generated and the at least one workpiece surface to be treated is disposed along a surface in the vacuum atmosphere on which the plasma density distribution, predetermined by the plasma beams, is generated. The method for production according to the invention is, on the other hand, distinguished in that in the vacuum atmosphere at least two plasma beams are generated with substantially parallel beam axes and a collection surface for the powder is disposed in the vacuum atmosphere such that on it a plasma density distribution predetermined by the plasma beams is generated.
It was found that in the prior known approach, in particular due to its cylindrical symmetry with respect to the axis of the one plasma beam, complex dependencies result of the concentration of reactive species on the radial distance from the beam axis. If in particular the local concentration, of critical importance for the generation of diamond material, of atomic hydrogen in the prior known approach and as a function of the radial distance from the plasma beam axis is considered, a model calculation according to FIG. 1 shows the concentration decrease with increasing radial distance, with the assumption of a linear distance dependence according to (a) and with the assumption of a quadratic distance dependence according to (b).
As explained, in FIG. 1 the concentration function is depicted along a plane E which is at a distance Xmin parallel to the plasma beam axis A and viewed along a straight line G in plane E perpendicular to the beam axis A. The distance measure is normalized with Xmin, the concentration measure with respect to the maximum concentration on plane E at site S of distance Xmin.
Based on this representation, the reason is evident of why the prior known procedure with respect to deposition rate distribution presents problems, especially with relatively large workpiece areas to be coated if the one workpiece surface under consideration, or the several workpieces, is (are) each not disposed with their corresponding surface in such a way that they are rotationally symmetric about the beam axis A.
These problems are significantly reduced through the method proposed according to the invention.
Definitions
In the present specification the expression xe2x80x9cworkpiece support surfacexe2x80x9d is used if, according to the invention a workpiece treatment, in particular coating, is being addressed. The expression xe2x80x9ccollection surfacexe2x80x9d is used if powder or cluster generation is being addressed. The general term xe2x80x9cdeposition surface or xe2x80x9cdeposition configurationxe2x80x9d is used if a xe2x80x9cworkpiece support surfacexe2x80x9d as well as also a xe2x80x9ccollection surfacexe2x80x9d jointly are being addressed.
In an especially preferred embodiment of the method according to the invention, onto the deposition surface a metastable material is deposited, preferably cBN, xcex1-Al2O3, C3N4 or, especially preferred, diamond.
In a further preferred embodiment of the method according to the invention, a silicon compound is deposited onto the deposition surface preferably microcrystalline silicon xcexcCxe2x80x94Si:H, and as a reactive gas silane is preferably employed.
In a preferred embodiment the plasma beams are realized as low-voltage arc discharges, highly preferred as high-current arc discharges, preferably by means of cold cathode discharges, but especially preferred by means of hot cathode discharges.
Further, the deposition surface is disposed in the vacuum atmosphere and with respect to the plasma beams such that along this surface predetermined minimum plasma density fluctuations occur. This is attained in particular thereby that along said deposition surface plasma densities of maximally 20% occur, preferably of maximally 10%, preferably even of maximally 5% of the plasma density maxima of the particular closest plasma beams, wherein further the plasma beams can be operated identically, i.e. in this case have substantially identical maximum plasma densities in their axes. But it is advantageous to optimize the plasma density distribution attained along deposition surfaces, for example of predetermined shape, through the specific tuning of the particular discharges, i.e. through the specific tuning of the beam-specific maximum plasma densities. For this purpose it is further proposed that the plasma beam discharges can be operated independently of one another, which opens the feasibility of carrying out said optimization specifically from case to case.
It was additionally and surprisingly found that with the proposed method a material deposition at very high deposition rates can be realized at temperatures at the deposition site of maximally 500xc2x0 C. Accordingly, the methods according to the invention are preferably carried out such that by disposing the deposition surface such that the plasma density maxima obtaining on it are 20% of the closest beam plasma density maxima, a deposition rate on the deposition surface of minimally 400 nm/min is set up, preferably at said temperature of maximally 500xc2x0 C.
In a further preferred embodiment, the plasma density distribution is tuned by means of at least one magnetic field parallel to the beam axis.
In a further preferred embodiment the plasma density distribution is tuned by means of at least one magnetic field parallel to the beam axes.
In a further preferred embodiment a gas flow is established substantially parallel to the beam axes.
In order to equalize even further the treatment effect, in particular the coating thickness distribution, on several workpieces to be treated, which can be of significance in particular in workpiece surface treatment, it is further proposed that the workpieces are rotated about axes of rotation and/or moved linearly at least approximately parallel to the beam axes, preferably in pendulum motions back and forth.
It was furthermore found that with the procedure according to the invention even further effectivity can be attained with respect to simultaneously treatable workpieces or deposited quantity of powder thereby that at least one first deposition surface is disposed between the plasma beams and at least a second deposition surface between the plasma beams and the wall of a treatment chamber with the vacuum atmosphere.
While, consequently, on the first deposition surface, which is between the plasma beams, material is deposited bilaterally, be that for obtaining powder or workpiece coating, on the second deposition surface material is deposited on only one side, be this again for obtaining powder or for treatment, such as in particular coating, of workpieces. With respect to workpieces, consequently, workpieces to be coated bilaterally or multilaterally, such as milling tools or drills, can be disposed along the first deposition surface, whereas workpieces, which require treatment, in particular coating, on only one side, such as indexable inserts, can be disposed along the second deposition surface. This increases decisively the efficiency of the method or of an installation provided for this purpose.
An installation according to the invention is now distinguished by the characterizing features of the invention and various embodiments of this installation are disclosed as well as, uses of this installation.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.